The Common House Roach, Blattella germánica Linn., as a Potential Vector of Salmonella typhimurium and Salmonella typhosa..

Summary Controlled feeding experiments conducted with adult specimens of Blattella germanica mounted on wax blocks are described. Roaches fed an exclusive diet of molar sucrose lived for periods up to 205 days with an average longevity of about 50 days. Diets consisting of beef heart infusion broth or a mixture of skim milk, yeast extract and sucrose were effective in maintaining the test insects over long periods of time. Prior to feeding the specific Salmonella cultures, so-called normal flora studies were carried out on the roaches, and the aerobic and facultative flora are presented. No anaerobic determinations were made. When S. typhimurium was fed to the individual roaches in sufficient numbers, positive stool cultures could be obtained up to the 7th day after feeding the test species, and the alimentary canal contents was found to harbor the viable organisms up to the 11th day after feeding. Controlled feeding of millions, even billions, of S. typhosa to mounted Blattella germanica failed to produce a single positive stool after 24 hours in all of the roaches tested, and between 12 and 15 hours after feeding massive doses of the typhoid organism, the alimentary canal contents showed only a single positive culture for this Salmonella species. Only two of the 45 stools passed by roaches fed the typhoid organisms were found to be positive. Both of these stools were passed within the first 18 hours after the massive feeding of the test organisms. None of the tests conducted revealed the presence of any lethal agent responsible for this mass destruction of S. typhosa.